Semiconductor device with a bipolar transistor formed in a layer of semiconductor material provided on an insulating substrate

Abstract

A semiconductor device with a bipolar transistor formed in a layer of semiconductor material (2) provided on an insulating substrate (1), in which material a collector zone (4), a base zone (5), and an emitter zone (6) are provided below a strip of insulating material (3) situated on the layer (2), which zones are connected to contact regions (7, 8, 9, 10) lying adjacent the strip (3), three of the contact regions (8, 9, 10) lying next to one another at a same side of the strip (3), of which two (8 and 9) are connected to the base zone (5) while the third (10), which lies between the former two (8 and 9), is connected to the emitter zone (6). The three contact regions (8, 9, 10) situated next to another at the same side of the strip (3) are provided alternately in the layer of semiconductor material (2) and in a further layer of semiconductor material (19) extending up to the strip (3). The three contact regions (8, 9, 10) connected to the base zone (5) and the emitter zone (6) may be provided with mutual interspacings which are smaller than the details which can be realised in a photoresist layer by means of the photolithographic process to be used in the manufacture of the transistor. As a result, the transistor can be manufactured with a very small extrinsic base.

We claim: 
     
       1. In a semiconductor device having a bipolar transistor formed in a layer of semiconductor material on an insulating substrate, said bipolar transistor having a collector zone, a base zone and an emitter zone disposed in said layer of semiconductor material, said semiconductor device also having a strip of insulating material disposed on said layer above said collector zone, said base zone and said emitter zone, and contact regions adjacent to one another at one side of said strip, two of said contact regions being connected to said base zone and a third of said contact regions being disposed between said two contact regions and being connected to said emitter zone, the improvement comprising: a further layer of semiconductor material different from said layer of semiconductor material, said further layer of semiconductor material being disposed on said insulative substrate, butting said layer of semiconductor material at said one side of said strip of insulating material, and further extending over a portion of said strip of insulating material at said one side, (i) one of either said third contact region or said two contact regions being disposed in said layer of semiconductor material and (ii) the other one of either said contact region or said two contact regions being disposed in said further layer of semiconductor material and being comprised of either a strip-shaped region or strip-shaped regions, respectively.   
     
     
       2. A semiconductor device according to claim 1, wherein said two of said contact regions connected to said base zone are disposed in said layer of semiconductor material, and wherein said third contact region connected to said emitter zone is disposed in said further layer of semiconductor material. 
     
     
       3. A semiconductor device according to claim 2, wherein a fourth contact region is disposed in said layer of semiconductor material at a second side of said strip of insulating material, said fourth contact region being connected to said collector zone and being disposed opposite to said third contact region. 
     
     
       4. A semiconductor device according to claim 3, wherein strongly doped zones are disposed in said base zone between said three contact regions. 
     
     
       5. A semiconductor device according to claim 3, wherein said collector zone has a constricted width below said strip of insulating material, said constricted width being substantially equal to width of said emitter zone. 
     
     
       6. A semiconductor device according to claim 5, wherein said collector zone widens out from said constricted width in a direction beyond said strip. 
     
     
       7. A semiconductor device according to claim 1, wherein a fourth contact region is disposed in said layer of semiconductor material at a second side of said strip of insulating material, said fourth contact region being connected to said collector zone and being disposed opposite to said third contact region. 
     
     
       8. A semiconductor device according to claim 1, wherein strongly doped zones are disposed in said base zone between said three contact regions. 
     
     
       9. A semiconductor device according to claim 1, wherein said collector zone has a constricted width below said strip of insulating material, said constricted width being substantially equal to width of said emitter zone. 
     
     
       10. A semiconductor device according to claim 9, wherein said collector zone widens out from said constricted width in a direction beyond said strip.